Liquid crystal display device

ABSTRACT

A liquid crystal display device has a liquid crystal layer between a glass substrate and a counter substrate. A TFT and scanning lines which control the TFT are provided on the glass substrate. On the counter substrate, a gradation signal line which is connected to a counter electrode applying a voltage to the liquid crystal layer is provided opposite to the scanning lines. A sealing section for sealing the liquid crystal of the liquid crystal layer is provided while enclosing the display area between the glass substrate and the counter substrate. The sealing section has conductive particles. Upper contact pads connected to the gradation signal lines and lower contact pads on the glass substrate are electrically connected via the conductive particles. This realizes a liquid crystal display device with a smaller frame and makes the mounting compact in size without causing poor connection due to line breakage.

FIELD OF THE INVENTION

The present invention relates to an active matrix liquid crystal displaydevice adopting switching elements such as MIM (metal insulator metal),TFT (thin film transistor).

BACKGROUND OF THE INVENTION

In recent years, a liquid crystal display device which consumes lesspower and has superior portability is often adopted as a display deviceof mobile phones. Especially, an STN-LCD (super twisted nematic-liquidcrystal display) having a simple structure and of lower cost is widelyadopted.

As shown in FIG. 17, the STN-LCD has a glass substrate 101 made of glassand a counter substrate 102 which are opposed via a liquid crystal layer(not shown). Further, a sealing section made of a sealing material forsealing the liquid crystal of the liquid crystal layer is provided so asto enclose the display area between the glass substrate 101 and thecounter substrate 102.

The glass substrate 101 includes common lines 103 which also act aspixel electrodes for applying a voltage to the liquid crystal layer. Thecommon line 103 is connected to a reference signal driver via a COMelectrode on the glass substrate 101. The counter substrate 102 includessegment lines 104 which also act as pixel electrodes. The segment line104 is connected to a gradation signal driver via a SEG electrode on thecounter substrate 2. Further, the common line 103 and the segment line104 are orthogonal, and both formed by a transparent conductive filmsuch as ITO.

Further, in a color STN-LCD, the common line 103 is formed on a colorfilter and on an overcoat which protects the color filter. The overcoatis easy to get a scratch. This may cause the transparent conductive filmwhich is formed on the overcoat to be the common line 103 to cut offeven by an indistinct scratch which can be made during manufacturingprocesses since the common line 103 and the segment line 104 are formedon different substrates. Further, adhesion between the overcoat and thetransparent conductive film made of ITO or the like is exceedingly weakin comparison with, for example, adhesion between glass and atransparent conductive film. Therefore, it is almost impossible tore-mount the reference signal driver and/or the gradation signal driverin the case where mounting is failed.

On the other hand, in a small or medium sized panel used for a displayof a mobile phone, commonly, an input terminal of the common line 103 isformed on the counter substrate 102. And the input terminal and thecommon line 103 are electrically connected by transfer technology usingconductive particles which are distributed in the sealing section.Hereinafter, this connection part is referred to as “a transfersection”. By thus electrically connecting the input terminal and thecommon line 103 via the transfer section, the common line 103 and thesegment line 104 can exist on a single substrate (the counter substrate102).

As described, since the common line 103 electrically transfers to thetransparent conductive film made of ITO or the like formed on thecounter substrate 102 via the conductive particles distributed in thesealing section, it prevents the cutoff of the common line 103, andalso, makes it possible to re-mount the reference signal driver and/orthe gradation signal driver in the mounting process. Further, since theinput terminal of the common line 103 is formed on the counter substrate102, the common line 103 and the segment line 104 can exist on a singlesubstrate (the counter substrate 102). This makes it possible to adopt asegment-common integral driver, and make the mounting compact in size.

However, in the foregoing STN-LCD, variation of contact resistancebetween the adjacent transfer sections is perceived as non-uniformdisplay. Therefore, when assuming the mean distribution volume of theconductive particle is D, and its distribution is σ, even when thedistribution density of the conductive particle is small like D-5σ, itis necessary to prevent contact resistance from being perceived asnon-uniform display by conserving the transfer section area as large aspossible and increasing the number of the conductive particle in thetransfer section.

Here, the following will explain the variation of distribution volume ofthe conductive particle.

As shown in FIG. 18, when the conductive particles are distributed, thedistribution is approximated by a normal distribution around the meandistribution volume D. When the volume of the conductive particle ismore than the mean volume D, it is possible to ensure stable connectionin the transfer section. In contrast, when the volume of the conductiveparticle is less than the mean volume D, connection in the transfersection, in other words, resistance in the transfer section variesdepending on the distribution volume of conductive particle. Table 1shows separation from the mean distribution volume D and probability ofexistence, regarding to the distributed conductive particles.(continued)

TABLE 1 PROBABILITY OF 16% EXISTENCE LESS THAN (D-σ) PROBABILITY OF 2.3% EXISTENCE LESS THAN (D-2σ) PROBABILITY OF  0.15% EXISTENCE LESSTHAN (D-3σ) PROBABILITY OF  6.3 × 1e⁻³% EXISTENCE LESS THAN (D-4σ)PROBABILITY OF  5.73 × 1e⁻⁵% EXISTENCE LESS THAN (D-5σ)

If assuming that the minimum particle density to prevent the contactresistance in the transfer section from being perceived as non-uniformdisplay is D₀, Table 1 shows that poor contact occurs at a rate of 0.15%when D₀=D−3σ. Namely, when a panel has 160 transfer sections, at leastone in 4.2 panels will show poor contact. Similarly, as shown in Table1, poor contact occurs at a rate of 5.73e⁻⁵% when D₀=D−5σ. In this case,when a panel has 160 transfer sections, at least one in 10908 panelswill show poor contact. Determination of the mean distribution volume Dis important in the distribution of the conductive particle, becausedistribution σ is automatically determined by the mean distributionvolume D, even though the distribution σ can be adjusted to some extentby using an automatic stirring device for stirring the sealing material.

The permitted limit of the STN-LCD for the contact resistance variationin the adjacent transfer sections becomes smaller, as the STN-LCD hashigh-precision (256 colors→4096 colors) and multi-gradation displays(6500 colors). Further, as the line width of sealing section becomesnarrower in accordance with high-precision and narrower frame (narrowernon-display area), the area of the transfer section becomes smaller.Accordingly, it is difficult to apply the technology of electrictransfer using the conductive particles distributed in the sealingsection to the STN-LCD in terms of high-precision, multi-gradationdisplays, and narrower frame (narrower non-display area) which are majorfactors for a mobile phone in next-generation.

Meanwhile, liquid crystal display devices of active driving type inwhich a switching element such as MIM or TFT of counter source structurehave been proposed as a liquid crystal display device (LCD) having asimple structure like the STN-LCD. These liquid crystal display devicesare more suitable for high-precision, multi-gradation displays, andnarrower frame which are major factors for a mobile phone innext-generation, in comparison with the STN-LCD.

FIG. 19 shows an example of an equivalent circuit of the arrangement ina conventional active matrix liquid crystal display device. In thisliquid crystal display device, pixel electrodes 111 are formed in amatrix manner on a transparent substrate which will be an active matrixsubstrate. Further, on the transparent substrate, a TFT 112 which is aswitching element is provided for each pixel electrode 111. In each TFT112, the pixel electrode 111 is connected to a drain electrode. And inthe TFTs 112 which are horizontally (in a column direction) aligned in adisplay screen, respective gate electrodes are connected to a samereference scanning line 113, and also are connected to the same dataline 114 in the TFTs 112 vertically (in a row direction) aligned in thedisplay screen. Namely, the respective scanning lines 113, and therespective data lines 114 in the above directions are orthogonallydisposed while surrounding the pixel electrode 111.

With the foregoing arrangement, the TFT 112 is controlled so as to turnon/off in response to the gate signal which is supplied via the scanningline 113. And when the TFT 112 is on, a data signal (display signal) issent to the pixel electrode 111 via the data line 114.

Further, each drain electrode of the TFTs 112 is individually connectedto the pixel electrode 111, and an electrode which forms an accumulationcapacitor 115, and the other electrode opposite to the former electrodevia an insulation layer is connected to a reference signal line 116. Theaccumulation capacitor 115 holds a voltage which is applied to theliquid crystal layer.

In the active matrix liquid crystal display device thus described, theliquid crystal layer is caught between the active matrix substrate andthe counter substrate which is opposite to the active matrix substrate.

However, in the active matrix liquid crystal display device shown inFIG. 19, poor connection due to the cutoff is likely to occur at acrossing section of the scanning line 113 and the data line 114 whichare orthogonally disposed on a single substrate. This decreases theyield, and increases the manufacturing cost.

This being the case, in order to solve these problems, a structurehaving data lines disposed on a counter substrate (hereinafter, referredto a counter matrix structure) has been conventionally proposed. Anexample of the arrangement of the counter matrix structure is shown inFIG. 20, FIGS. 21(a) through 21(d).

In this type of liquid crystal display device, pixel electrodes 124 areprovided in a matrix manner on a glass substrate 120, and TFTs 121 areformed on the respective pixel electrodes 124. The drain electrode (orthe source electrode) of each TFT 121 is connected to the pixelelectrode 124, and the gate electrode is connected to a same scanningline 122 among the TFTs 121 which are horizontally (in a columndirection) aligned in a display screen. These arrangements are the sameas those of the liquid crystal display shown in FIG. 19. However, incontrast, the source electrode (or the drain electrode) of each of theTFTs 121 which are horizontally (in a column direction) aligned in thedisplay screen is connected to a same reference signal line 123 insteadof connected to the data line 114 where a data signal is applied, unlikethe liquid crystal display device shown in FIG. 19. And gradation signallines 126 are orthogonally disposed to scanning lines 122 of the glasssubstrate 120 on a counter substrate 125 which is opposite to the glasssubstrate 120 via a liquid crystal layer. Note that, in thisarrangement, each gradation signal line 126 also acts as a counterelectrode at the portion opposite to the pixel electrodes 124.

In the active matrix liquid crystal display device having the countermatrix structure thus described, since the crossing sections of thescanning line 122 and the gradation signal line 126 do not exist on asingle substrate, the foregoing problems: decreases of the yield andreliability caused by poor connection due to the cutoff can be solved.

However, according to the arrangement shown in FIG. 20, FIGS. 21(a)through 21(d), since the scanning line 122 and the gradation signal line126 are formed on respective substrates, the gradation signal line 126made of a transparent conductive film of ITO or the like formed on anovercoat 131 (see FIG. 21(d)) may cut off even by an indistinct scratchwhich can be made during manufacturing processes. Further, adhesionbetween the overcoat 131 and the gradation signal line 126 isexceedingly weak in comparison with, for example, adhesion between theglass substrate 120 and the gradation signal line 126 made oftransparent conductive film. Therefore, it is almost impossible tore-mount these liquid crystal display elements during a mounting processin the case where mounting is failed.

This being the case, a transparent conductive film (gradation signalline 126) made of ITO or the like is formed on a glass (glass substrate120) by selectively removing the overcoat 131, to which havingphotosensitivity has been given, of the mounting part. This will solvethe foregoing problems; however, the transmission rate of the overcoat131 decreases due to its photosensitivity, and the transmission rate orthe reflectance of the liquid crystal panel decreases. Further, an extraprocess for selectively removing the overcoat 131 is required. Moreover,the transparent conductive film of ITO or the like may cut off becauseof the difference in level between the portion having the overcoat 131and the portion having no overcoat 131.

As shown in FIG. 21(b), a counter electrode 128 and an input terminal127 are connected to the gradation signal line 126 on the countersubstrate 125. Further, in addition to the arrangement shown in FIG. 20,a gate insulation film 135 (see in FIG. 21(d)), an input terminal 130connected to the gradation signal line 123, and an input terminal 129connected to the scanning line 122 (see in FIG. 21(a)) are formed on theglass substrate 120. Further, a sealing section 134 which seals liquidcrystal has spacers 136, and its cell thickness is held by the diameterof the spacer 136.

Furthermore, since the scanning line 122 and the gradation signal line126 are formed on respective substrates, the input terminal 127 and theinput terminal 129 are also formed on respective substrates. Therefore,as shown in FIG. 21(c), the liquid crystal element becomes bulky whenTAB 133 is mounted, and it is impossible to adopt a compact mountingsuch as COG.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a liquid crystaldisplay device with smaller frame and the compact mounting in sizewithout causing poor connection due to cutoff.

In order to attain the foregoing object, a liquid crystal display deviceaccording to the present invention includes a switching elementsubstrate having switching elements, a counter substrate opposite to theswitching element substrate, a liquid crystal layer formed between thesubstrates, a sealing section having conductive particles and providedso as to enclose a display area between the substrates for sealingliquid crystal constituting the liquid crystal layer, first signalwiring provided on one of the substrates for controlling the switchingelement, second signal wiring opposite to the first signal wiring andprovided between the substrates for applying a voltage to the liquidcrystal layer, and at least one transfer section for electricallyconnecting the first signal wiring or the second signal wiring and thesubstrate opposite to the first signal wiring or the second signalwiring via the conductive particles.

With the foregoing structure, the first signal wiring or the secondsignal wiring, and a substrate opposite to the first signal wiring orthe second signal wiring, are electrically connected via the conductiveparticles by the transfer section. Namely, the first signal wiring andthe substrate opposite to the first signal wiring, or the second signalwiring and the substrate opposite to the second signal wiring areelectrically connected. Commonly, active driving has a wider permittedlimit of contact resistance variation in the adjacent transfer sectionsthan that of passive driving. Therefore, it becomes possible to providea liquid crystal display device of lower cost since active drivingrequires less volume of the conductive particles than that of passivedriving.

Additional objects, features, and strengths of the present inventionwill be made clear by the description below. Further, the advantages ofthe present invention will be evident from the following explanation inreference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a plan view showing an arrangement of the major part of aglass substrate used for a liquid crystal display device according toone embodiment of the present invention.

FIG. 1(b) is a plan view showing an arrangement of relevant part of acounter substrate used for the liquid crystal display device.

FIG. 1(c) is a plan view showing an arrangement of relevant part of theliquid crystal display device.

FIG. 1(d) is a cross-sectional view, taken along the line A-A′ of FIG.1(c).

FIG. 1(e) is a cross-sectional view, taken along the line B-B′ of FIG.1(c).

FIG. 2(a) is a drawing showing a transfer section of the liquid crystaldisplay device of FIGS. 1(a) through 1(e) in detail.

FIG. 2(b) is a cross-sectional view, taken along the line C-C′ of FIG.2(a).

FIG. 2(c) is a cross-sectional view, taken along the line D-D′ of FIG.2(a).

FIG. 2(d) is a drawing showing a staggered arrangement of the transfersection of the liquid crystal display device of FIGS. 1(a) through 1(e).

FIG. 2(e) is a cross-sectional view, taken along the line E-E′ of FIG.2(d).

FIG. 2(f) is a cross-sectional view, taken along the line F-F′ of FIG.2(d).

FIG. 3(a) is an explanatory view showing a potential of a scanningsignal, and a gradation signal or a reference signal, in active driving.

FIG. 3(b) is an explanatory view showing an input waveform of agradation signal line in active driving.

FIG. 3(c) is an explanatory view showing potentials of a common line anda segment line in the case of black display in passive driving.

FIG. 3(d) is an explanatory view showing potentials of a common line anda segment line in the case of white display in passive driving.

FIG. 3(e) is an explanatory view showing input waveforms of signals tothe common line and the segment line in passive driving.

FIG. 4 is a graph showing a relation between width of the transfersection and mean distribution volume of the conductive particles.

FIG. 5 is an explanatory view showing how a pressure test is carriedout.

FIGS. 6(a) through 6(c) are explanatory views showing behavior of theconductive particles in a sealing material during a process of combiningsubstrates.

FIG. 6(d) is a drawing showing a detailed arrangement of the sealingsection after the substrates are combined.

FIG. 7 is a cross-sectional view schematically showing a portion aroundthe transfer section in the case where a lower contact pad and an uppercontact pad are both made of ITO in the liquid crystal display device ofFIGS. 1(a) through 1(e).

FIG. 8(a) is a drawing showing the transfer section in detail in thecase where the lower contact pad and the upper contact pad are both madeof ITO.

FIG. 8(b) is a cross-sectional view, taken along the line G-G′ of FIG.8(a).

FIG. 8(c) is a cross-sectional view, taken along the line H-H′ of FIG.8(a).

FIG. 8(d) is a drawing showing a staggered arrangement of the transfersection of FIG. 8(a) in detail.

FIG. 8(e) is a cross-sectional view, taken along the line I-I′ of FIG.8(d).

FIG. 8(f) is a cross-sectional view, taken along the line J-J′ of FIG.8(d).

FIG. 9(a) is a plan view showing an arrangement of relevant part of theglass substrate used for the liquid crystal display device of FIGS. 1(a)through 1(e) in the case where an insulation film is formed in thesealing section.

FIG. 9(b) is a plan view showing an arrangement of relevant part of theliquid crystal display device in the case where the insulation films areformed in the sealing section.

FIG. 9(c) is a cross-sectional view, taken along the line K-K′ of FIG.9(b).

FIG. 9(d) is a cross-sectional view, taken along the line L-L′ of FIG.9(b).

FIG. 10(a) is a drawing showing a transfer section of the liquid crystaldisplay device of FIGS. 9(a) through 9(d) in detail.

FIG. 10(b) is a cross-sectional view, taken along the line M-M′ of FIG.10(a).

FIG. 10(c) is a cross-sectional view, taken along the line N-N′ of FIG.10(a).

FIG. 10(d) is a drawing showing a staggered arrangement of the transfersection of the liquid crystal display device of FIGS. 9(a) through 9(d)in detail.

FIG. 10(e) is a cross-sectional view, taken along the line O-O′ of FIG.10(d).

FIG. 10(f) is a cross-sectional view, taken along the line P-P′ of FIG.10(d).

FIG. 11 is a cross-sectional view schematically showing a portion aroundthe transfer section in the case where on insulation film is formed inthe sealing section on the glass substrate and the lower contact pad andthe upper contact pad are both made of ITO.

FIG. 12(a) is a plan view showing an arrangement of the glass substratewhen a driving IC is provided as a single chip.

FIG. 12(b) is a plan view showing an arrangement of the liquid crystaldisplay device when a driving IC is provided as a single chip.

FIG. 13(a) is a plan view showing an arrangement of relevant part of aglass substrate used for a liquid crystal display device according toanother embodiment of the present invention.

FIG. 13(b) is a plan view showing an arrangement of relevant part of acounter substrate used for the liquid crystal display device of FIG.13(a).

FIG. 13(c) is a plan view showing an arrangement of relevant part of theliquid crystal display device of FIG. 13(a).

FIG. 13(d) is a cross-sectional view, taken along the line Q-Q′ of FIG.13(c).

FIG. 13(e) is a cross-sectional view, taken along the line R-R′ of FIG.13(c).

FIG. 14(a) is a plan view showing an arrangement of relevant part of theglass substrate used for the liquid crystal display device of FIGS.13(a) through 13(e) in the case where an insulation film is formed inthe sealing section.

FIG. 14(b) is a plan view showing an arrangement of relevant part of theliquid crystal display device in the case where the insulation film isformed.

FIG. 14(c) is a cross-sectional view, taken along the line S-S′ of FIG.14(b).

FIG. 14(d) is a cross-sectional view, taken along the line T-T′ of FIG.14(b).

FIG. 15(a) is a plan view showing an arrangement of relevant part of aglass substrate used for the liquid crystal display device according toyet another embodiment of the present invention.

FIG. 15(b) is a plan view showing an arrangement of relevant part of acounter substrate used for the liquid crystal display device of FIG.15(a).

FIG. 15(c) is a plan view showing an arrangement of relevant part of theliquid crystal display device of FIG. 15(a).

FIG. 15(d) is a cross-sectional view, taken along the line U-U′ of FIG.15(c).

FIG. 15(e) is a cross-sectional view, taken along the line V-V′ of FIG.15(c).

FIG. 16 is a cross-sectional view schematically showing a portion aroundthe transfer section in the case where the lower contact pad and theupper contact pad are both made of ITO in the liquid crystal displaydevice of FIGS. 15(a) through 15(e).

FIG. 17 is an exploded perspective view showing an arrangement of aconventional STN-LCD.

FIG. 18 is a distribution view showing a frequency of the distributionvolume of conductive particles.

FIG. 19 is an equivalent circuit diagram of a conventional active matrixliquid crystal display device having a structure in which a commonelectrode is provided on a counter substrate.

FIG. 20 is an exploded perspective view of a conventional active matrixliquid crystal display device having a counter matrix structure in whicha data line is provided on a counter substrate.

FIG. 21(a) is a plan view schematically showing an arrangement of aglass substrate of the active matrix liquid crystal display device shownin FIG. 20.

FIG. 21(b) is a plan view schematically showing an arrangement of acounter substrate of the active matrix liquid crystal display deviceshown in FIG. 20.

FIG. 21(c) is a plan view showing an arrangement when a TAB is mountedonto the active matrix liquid crystal display device shown in FIG. 20.

FIG. 21(d) is a cross-sectional view, taken along the line W-W′ of FIG.21(c).

FIG. 22 is a graph showing a correlation between the average number ofthe conductive particles in the transfer section and occurrence ofdefect liquid crystal panels.

DESCRIPTION OF THE EMBODIMENTS

[First Embodiment]

The following will explain one embodiment of the present invention withreference to FIGS. 1 through 12, and FIG. 17.

As shown in FIG. 1(e), a liquid crystal display device includes a glasssubstrate 1 made of glass (a substrate having switching elements, firstsubstrate) and a counter substrate 2 (second substrate) which areopposed via a sealing section 3, the both substrates 1 and 2 are sealedwith liquid crystal constituting a liquid crystal layer 4 as a mediumlayer.

Further, on the glass substrate 1 which is an active matrix substrate,thin film transistors 11 (hereinafter referred to as a TFT), pixelelectrodes 9, reference signal lines 10 and lower contact pads 12 (firstcontact pad) are provided. Note that, the TFT 11 includes a scanningline 5 (first signal wiring), a drain electrode 6, a reference electrode7 and a silicon nitride film 8.

The pixel electrodes 9 are disposed in a matrix manner, and the TFT 11which is a switching element having three terminals is provided for eachpixel electrode 9. TFTs 11 are also disposed in a matrix mannercorresponding to the pixel electrodes 9.

In the TFT 11 which are horizontally (in a column direction) aligned inthe display, the gate electrodes are connected to the same scanning line5. The pixel electrodes 9 are connected to the drain electrodes 6.Further, in the TFTs 11 which are horizontally (in a column direction)aligned in the display, reference electrodes 7, which are sourceelectrodes of the TFTs 11, are connected to the same reference signalline 10.

Further, an intrinsic semiconductor layer and an active semiconductorlayer (not shown) are formed on the gate electrodes. The intrinsicsemiconductor layer is a channel section of the TFTs 11, and also acurrent path connecting the drain electrode 6 and the referenceelectrode 7 which are formed thereon. The active semiconductor layerexecutes contact between the drain electrodes 6 and the referenceelectrodes 7.

The silicon nitride film 8 is a gate insulation film which is formed onsubstantially the entire surface of the glass substrate 1 so as to coverthe scanning lines 5. The silicon nitride film 8 includes an opening 8a. The reference signal lines 10 are partly exposed in the opening 8 ato be connected to the reference electrodes 7.

The reference electrodes 7, the drain electrodes 6 and the pixelelectrodes 9 are made of a transparent conductive film such as ITO(Indium Tin Oxide) or the like.

The scanning lines 5 are disposed parallel to the reference signal lines10, and as shown in FIG. 1(c), input terminals 5 a of the scanning lines5 and input terminals 10 a of the reference signal lines 10 areconnected to a driving IC 22 (first signal generation circuit).

Further, as shown in FIG. 1(a), the lower contact pads 12 are disposedso as to enclose a display area 29, parallel to the scanning lines 5.The lower contact pads 12 form a transfer section 24 in conjunction withupper contact pads 16 (described later), and are connected to inputterminals 15 a of gradation signal lines 15 (described later) which areconnected to a driving IC 23 (second signal generation circuit) (seeFIG. 1(c)). Here, the input terminals 15 a of the gradation signal lines15 also act as routing wiring of the gradation signal lines 15.

The scanning lines 5, the input terminals 5 a, the reference signallines 10, the input terminals 10 a, the lower contact pads 12 and theinput terminals 15 a are all made of Ta, and are formed in the samemanufacturing step.

Note that, the scanning lines 5, the input terminals 5 a, the referencesignal lines 10, the input terminals 10 a, the lower contact pads 12 andthe input terminals 15 a may be made of any kinds of metal, for example,Al, Cr, Ti, Mo, Cu or the like.

On the other hand, as shown in FIG. 1(e), a color filter layer 18 havingcolor filters of red, blue, green and a black matrix is provided on thecounter substrate 2. An overcoat film 19 is formed so as to cover thecolor filter 18. Further, the gradation signal lines 15 (second signalwiring), upper contact pads 16(second contact pad) and counterelectrodes 17 are formed on the overcoat film 19.

The gradation signal lines 15 are data lines to which a data signal issupplied, and are orthogonally disposed to the scanning lines 5 on theglass substrate 1. In this arrangement as shown in FIG. 1(b), thegradation signal lines 15 also act as the counter electrodes 17 at theportion opposite the pixel electrodes 9, and also, act as the uppercontact pads 16 at the portion opposite the lower contact pads 12.

The gradation signal lines 15 are made of transparent conductive filmsuch as ITO or the like. Namely, the counter electrodes 17 aretransparent electrodes made of ITO or the like. The counter electrodes17 and the pixel electrodes 9 are opposed via the liquid crystal layer4, and the counter electrodes 17 drive the liquid crystal in conjunctionwith the pixel electrodes 9. Further, the upper contact pads 16 are alsomade of a transparent conductive film such as ITO or the like.

Further, as shown in FIG. 1(a), the sealing section 3 for sealing theliquid crystal makes up the liquid crystal layer 4 is provided so as toenclose the display area 29 which between the glass substrate 1 and thecounter substrates 2. The sealing section 3 is made of a sealingmaterial of ultraviolet setting resin and has spacers 21 and conductiveparticles 20 as shown in FIG. 1(d). It is preferable that the sealingmaterial is a thermosetting epoxy resin for example.

The transfer section 24 is made up of the conductive particles of thesealing section 3, the lower contact pads 12, and the upper contact pads16.

The following will explain the details of the transfer section 24.

The spacers 21 of the sealing section 3 controls the cell thicknessaccording to its diameter. The spacers 21 is made of glass or the like,and is not elastic. It is preferable that the spacers 21 as a sealingmaterial is made of, for example, a glass fiber having a diameter of 6μm, which is contained at the proportion of 1 wt %. The thickness of thecell is determined by the diameter of the spacers 21 which exists in thethickest area of the sealing section 3.

Further, the conductive particles 20 have a diameter greater than thatof the spacers 21, and made of, for example, a spherical elastic resinparticle coated with a conductive material such as Ni, Au or the like.It is preferable that the sealing material is prepared by deaeratingresin particles having s gold-plated surface of about 0.1 μm, and evenlymixing them with elastic conductive particles 20 to 1 wt %, for example.

The upper contact pads 16 are electrically connected to the lowercontact pads 12 via the conductive particles 20. Namely, the gradationsignal lines 15 transfer to the glass substrate 1 via the transfersection 24.

The following will explain the behavior of the conductive particles 20in the sealing material when combining the glass substrate 1 and thecounter substrate 2, with reference to FIGS. 6(a) through 6(c).

A thermosetting material to make up the sealing section 3 is prepared bymixing and stirring the spacers 21 and the conductive particles 20 inthe thermosetting material until the spacers 21 and the conductiveparticles 20 are evenly distributed in the material. Thereafter, thesealing material is applied on, for example, the glass substrate 1, forexample, by printing (FIG. 6(a)). Here, the conductive particles 20 aredistributed while being stacked one over another in the sealingmaterial.

Next, after the glass substrate 1 and the counter substrate 2 are mated,suitable pressure is applied to deform the conductive particles 20 (FIG.6(b)). At this point, the conductive particles 20 are distributed atrandom on a single surface as the sealing material spreads in the celluntil the thickness of the cell becomes the same as the diameter of theconductive particles 20.

The conductive particles 20 are further deformed when more pressure isapplied (FIG. 6(c)). Then, the conductive particles 20 are fixed inposition when they are deformed to the thickness approximately equals tothe cell thickness to be held by the spacers 21, i.e., the diameter ofthe spacers 21.

Here, the sealing section 3 also spreads as the conductive particles 20are deformed, and it stops spreading when the conductive particles 20are deformed to the thickness approximately equal to the cell thicknessto be held by the spacers 21. The glass substrate 1 and the countersubstrate 2 in this state are bonded and fixed by heating. Note that,FIG. 6(d) is a plan view of the sealing section 3 as viewed from theside of the glass substrate 1. Further, the conductive particles 20 arerequired to have a size or a diameter greater than the cell thickness,i.e., the distance between the upper contact pad 16 and the lowercontact pad 12, so that the conductive particles 20 can slightly bedeformed at a portion where the upper contact pads 16 and the lowercontact pads 12 are electrically connected to each other.

This makes it possible to create an area W1 (see FIG. 6(d)) of the edgeof the sealing section 3 where the conductive particles 20 do not exist.Note that, the area W1 varies depending on the applied volume of thesealing material, the diameter of the conductive particles 20 and thediameter of the spacers 21. Here, in the case where the conductiveparticles 20 and the spacers 21 have the same diameter, the area W1cannot be created since the conductive particles 20 are not deformed andthe sealing section 3 does not spread. Accordingly, the diameter of theconductive particles 20 must be greater than that of the spacers 21.

Note that, the input terminals 5 a, 10 a and 15 a may be provided on thecounter substrate 2. In this case, the scanning lines 5 and thereference signal lines 10 transfer to the counter substrate 2 via thetransfer section 24.

As described, since the glass substrate 1 and the counter substrate 2are bonded and fixed, the elastic conductive particles 20 are deformedto some extent between the glass substrate 1 and the counter substrate 2as shown is FIG. 1(e). This makes it possible to provide a sufficientcontact area for the upper contact pads 16 and the lower contact pads12, thereby ensuring desirable electrical conduction. Consequently, itis possible to reduce the contact resistance between the upper contactpads 16 and the lower contact pads 12, thereby suppressing blunting ofsignals to the gradation signal lines 15.

Further, generally, in comparison with STN-LCDs, a voltage-hold typeliquid crystal display element which is used for active matrix liquidcrystal display devices shows greater degradation of image qualitycaused by degradation with time of the voltage-hold capability forliquid crystal. The degradation with time of voltage-hold capability forliquid crystal is caused by flowing out of impurities from the sealingmaterial, or ionization of ions.

However, as described, when the area W1 which does not have theconductive particle 20 is created at the edge of the sealing section 3,and when the width of the area W1 is at or greater than 50 μm, in otherwords, when the conductive particles 20 are provided only in the areawhich is at least 50 μm far from the interface between the liquidcrystal layer 4 and the sealing section 3, it is possible to prevent adecrease in voltage-hold capability for liquid crystal and non-uniformdisplay in the vicinity of the sealing section 3, which are caused byelution of impurities from the sealing material, or ionization of ions.Therefore, the degradation with time of voltage-hold capability forliquid crystal can be prevented, thereby making it possible to provide aliquid crystal display with stable reliability. Further, contaminationdoes not occur in manufacture since the conductive particles 20 do notseep out of the sealing section 3.

Note that, the transfer sections 24 may be disposed parallel to thescanning lines 5 as shown in FIG. 1(c), FIG. 2(a). However, in the casewhere the transfer sections 24 have a narrow pitch and are required toperform transfer in a small area, the transfer section 24 may have astaggered arrangement as shown in FIG. 2(d). To be more specific, thetransfer sections 24 may be disposed alternately along the both edges ofthe width of the sealing section 3, and the width of the gradationsignal lines 15 may be narrower than that of the upper contact pads 16.

Further, the transfer section 24 is provided between the driving IC 23,and the gradation signal lines 15 and the scanning lines 5. This makesit possible to downsize a routing wiring section of the gradation signallines 15 and thus reduce the frame area (non-display area) in the liquidcrystal display device, thereby realizing a liquid crystal displaydevice with a smaller frame.

As described, the input terminals 15 a of the gradation signal lines 15,the input terminals 5 a of the scanning lines 5 and the input terminals10 a of the reference signal lines 10 are provided on the glasssubstrate 1. This makes it possible to mount both the driving IC 22 andthe driving IC 23 on the glass substrate 1, in other words, it ispossible to mount those on a single substrate.

Accordingly, in the mounting process of a TAB (tape automated bonding)on a liquid crystal panel which is a base substrate of the driving ICs22 a and 23 a, it becomes possible to continuously mount the driving ICs22 and 23, which are for inputting signal voltages to the scanning lines5, the reference signal lines 10 and gradation signal lines 15, on aportion of the input terminals 15 a, 5 a and 10 a to be connected to thedriving ICs 22 a and 23 a, without turning over the liquid crystaldisplay element. Also, it is possible to mount a TAB for inputtingsignal voltages to the scanning lines 5, the reference signal lines 10and gradation signal lines 15, on a connecting portion of the TAB. Thisincreases the efficiency of mounting procedure, thereby reducingmanufacturing cost.

Further, since the input terminals (15 a, 5 a, 10 a) for wires bearingthe driving IC 22 and 23, the TAB, etc., are provided on a singlesubstrate, by the wire routing shown in FIGS. 12(a) and 12(b), thedriving IC 26 can be provided as a single chip. This makes the mountingcompact in size, thereby reducing the cost of the element required forthe driving IC 26 and manufacturing cost.

Further, it is possible to provide the input terminals 15 a on the glasssubstrate 1 made of glass (on the glass surface, or on an organic filmdeposited on the glass substrate) instead of providing it on theovercoat film 19 made of resin and formed on the counter substrate 2.This improves the mechanical strength and the adhesion between the inputterminals 15 a and the glass substrate 1, and also protects theterminals from breakage when handling. Also, this makes re-work ofmounting easier in case of mounting of the TAB, etc. is failed, therebyimproving the yield.

Further, as with the terminals 5 a and the terminals 10 a, the inputterminals 15 a are made of a metal film such as Ta or the like on theglass substrate 1 which has the TFTs 11. Generally, since a metal filmis of a smaller resistance than a transparent conductive film such asITO, it is possible to narrow the width of the terminals 15 a, in otherwords, it is possible to narrow a wiring pitch and create a COG (Chip onglass) structure with a narrow pitch, as compared with the case wherethe input terminals 15 a are made of a transparent conductive film suchas ITO, which is the same material used for the counter electrodes 17and the gradation signal lines 15, on the counter substrate 2. Further,it also is possible to reduce the frame area (non-display area) of theliquid crystal display element, i.e., a narrow frame is attained. Thisprovides a liquid crystal display device with a narrower frame, makesthe mounting compact in size, and reduces the mount area.

Further, since the scanning lines 5 and the gradation signal lines 15 donot intersect on a single substrate, poor connection due to breakage ofthose wires does not occur, and the yield is improved, thereby providinga liquid crystal display device with high reliability.

The following will explain a driving principle of liquid crystal.

The liquid crystal display device sequentially scans timeshared displaydata along the scanning lines 5 to display an image on a screen.

For example, when a scanning line 5 is horizontally scanned, a gatevoltage for turning on the TFTs 11 is applied to this scanning line 5.Meanwhile, a gate voltage for turning off the TFTs 11 is applied to theother scanning lines 5. Thus, when a scanning line 5 is horizontallyscanned, only the TFTs 11 of this scanning line 5 are turned on, and apixel voltage which is applied to the reference signal lines 10 isapplied to the pixel electrodes 9 of the scanning line 5 via thereference electrode, which is a source electrode, and the drainelectrode 6. At this time, the charge supplied to the pixel electrodes 9is accumulated in a capacitor. Further, a signal voltage (data signal)applied to the gradation signal lines 15 is applied to the liquidcrystal layer 4 by the counter electrode 17. With these processes, theliquid crystal on each pixel electrode 9 is driven by the potentialdifference between the pixel voltage applied to the pixel electrode 9,and the signal voltage applied to the counter electrode 17.

The following will explain an example of the manufacturing processes ofthe liquid crystal display device.

Firstly, a metal film of Ta or the like is deposited on the glasssubstrate 1 by a sputtering method. Then, the metal film is patternedinto a desired shape by a photo-lithography method, so as to form thescanning lines 5, an input terminal 5 a of the scanning lines 5, thereference signal lines 10, the input terminals 10 a of the referencesignal lines 10, the lower contact pads 12 and the input terminals 15 aof the gradation signal lines 15. Here, the input terminals 15 a and thelower contact pads 12 are formed into a continuous pattern to beelectrically conductive each other.

Secondly, a silicon nitride film 8 is deposited on the substantially theentire surface of the glass substrate 1 so as to cover the scanninglines 5 using plasma CVD (Chemical Vapor Deposition). Thereafter, thesilicon nitride film 8 is patterned by the photo-lithography method soas to remove the area of the silicon nitride film 8 on the inputterminals 5 a, the input terminals 10 a, the input terminals 15 a, andthe reference electrodes 7 where the reference signal lines 10 will beformed later. Thus, an opening 8 a is formed on the area of thereference signal lines 10 where the reference electrodes 7 will beformed.

Next, the intrinsic semiconductor layer (not shown) made of non-dopedamorphus silicon, and the active semiconductor layer doped with P(phosphor) are continuously deposited using plasma CVD on the scanninglines 5, or the gate electrodes (not shown) which are electricallyconnected to the scanning lines 5. Then, the intrinsic semiconductorlayer and the active semiconductor layer are patterned into land shapesby the photo-lithography method.

Next, after depositing an ITO film, which is a transparent conductivefilm by a sputtering method, the ITO film is patterned into a desirableshape using a photo-lithography method, so as to form the referenceelectrodes 7, the drain electrodes 6 and the pixel electrodes 9. At thistime, a portion (channel section) of the active semiconductor layerbetween the reference electrodes 7 and the drain electrodes 6 isremoved. Here, the drain electrodes 6 and the pixel electrodes 9 areformed into a continuous pattern to be electrically conductive eachother. Further, since the opening 8 a is provided by removing thesilicon nitride film 8 on the area of the reference signal lines 10where the reference electrodes 7 will be formed, the referenceelectrodes 7 are electrically connected to the reference signal lines10.

With the foregoing processes, the TFTs 11 made up of the scanning lines5, the drain electrodes 6 and the reference electrodes 7 can be formedtogether with the reference signal lines 10, the pixel electrodes 9, theinput terminals 5 a, 10 a, 15 a, and the lower contact pads 12.

Further, an alignment film (not shown) is formed by printing, and isaligned by rubbing. Then, plastic beads (not shown), which are spacersto keep the cell thickness in the display area 29 even, are distributedover the alignment film.

Meanwhile, after the ITO film which is a transparent conductive film isdeposited on the counter substrate 2 by a sputtering method, the ITOfilm is patterned into a desirable shape using a photo-lithographymethod so as to form the counter electrodes 17, the gradation signallines 15 and the upper contact pads 16. Here, the counter electrodes 17,the gradation signal lines 15 and the upper contact pads 16 are formedinto a continuous pattern to be electrically conductive each other. Notethat, at this time, the counter substrate 2 should have a color filterlayer 18 made up of a black resin layer and color layers of red, blueand green, and an overcoat film 19 made of flat and chemical resistantresin, which are formed on the counter substrate 2 in advance. Further,an alignment film (not shown) is formed by printing, and then aligned byrubbing.

Next, the counter substrate 2 is coated with a sealing material byprinting, and then combined with the glass substrate 1 after pre-bakingthe counter substrate 2 for 10 minutes at 110° C. Thereafter, the twosubstrates are calcined for about 90 minutes at 180° C. while applying 2kg/cm² pressure. Further, the two substrates are sealed with a sealingmaterial after injecting liquid crystal between them. Through theforegoing processes, the glass substrate 1 and the counter substrate 2are bonded and fixed to be completed as a liquid crystal panel. Notethat, a dispenser may be used to coat the counter substrate 2 with thesealing material.

Next, after a test for checking the lightning of the liquid crystalpanel, the driving IC 22 is mounted on the input terminals 5 a and 10 a,and also, the driving IC 23 is mounted on the input terminals 15 a toform the liquid crystal display element.

Further, polarizers (not shown) are provided on the both sides of theliquid crystal display element, and a light source made up of a coldcathode tube, a diffusing plate, a light guide plate, a reflector, acontrol substrate, etc., are provided to complete the liquid crystaldisplay device.

In this manner, since the terminals 15 a can be formed in the process offorming the scanning lines 5 and the reference signal lines 10, an extramanufacturing step will not be necessary.

The following will explain distribution volume of the conductiveparticles 20 in the sealing section 3. The volume of the conductiveparticles 20 to be distributed in the sealing section 3 is determined bya permitted limit of resistance variation in the transfer sections 24and the number of the conductive particles 20 which causes a decrease ofadhesion of the sealing section 3, a decrease of evenness of the cellthickness, and an increase of leakage between the wiring caused byaggregation of the conductive particles 20.

Firstly, the following will explain how the permitted limit of signaldelay caused by resistance variation at the transfer sections 24 betweenadjacent wires becomes different in passive driving as in the STN-LCDshown in FIG. 17, and in active driving as in the liquid crystal displaydevice of the present embodiment shown in FIGS. 1(a) and 1(b), indeciding the mean distribution volume of the conductive particles 20.

In the case of active driving, as shown in FIG. 3(a), when the signal ofthe scanning line 5 is on, the counter electrode 17 and the pixelelectrode 9 are charged to the same potential as that of the gradationsignal line 15 or the reference signal line 10. Accordingly, thegradation of liquid crystal display element is determined by the finalpotential of the gradation signal line 15 or the reference signal line10 when the signal of the scanning line 5 turns off. Therefore, in anyof delay 1, delay 2 and delay 3 shown in FIG. 3(b), the gradation of theliquid crystal display element will be the same as long as the finalpotential is the same. However, when the final potential is different asindicated by delay 4, the gradation of the liquid crystal displayelement will be different. Nevertheless, even when there is a slightvariation in contact resistance between adjacent wires (adjacenttransfer sections 24), the displayed gradation of the liquid crystaldisplay element will be the same as long as the final potential is thesame, and uniformity of the display will not be lost even in thepresence of a difference in signal delay.

On the other hand, as shown in FIGS. 3(c) and 3(d), in passive driving,gradation is expressed by the potential difference between the commonlines 103 (see FIG. 17) and the segment lines 104 when the common lines103 is on. Therefore, the dynamic range, which is the difference in theeffective values of the white display and the black display is around0.2 V, which is only {fraction (1/20)} of that of active driving at 4 v.Further, as shown in FIG. 3(e), since the amplitude of a common signalof the common lines 103 is large in passive driving, the differencebetween delay 1 and delay 2 greatly affects the effective value of theliquid crystal.

In this manner, in passive driving, a difference of signal delay causedby a small variation of contact resistance between adjacent wires(adjacent segment lines 104) impairs uniformity of the display to causenon-uniform of the display. Note that, in passive driving, the commonlines 103 corresponds to the scanning lines 5 in active driving, and thesegment line 104 corresponds to the gradation signal lines 15 in activedriving.

Aa described, the active driving has a wider permitted limit ofvariation of signal delay between adjacent wires, i.e., a widerpermitted limit for the variation of contact resistance.

Next, FIG. 4 shows how the permitted limit of variation differs inactive driving and passive driving, and the required mean distributionvolume of the conductive particles 20 for each driving.

Here, FIG. 4 assumes that the shape of the transfer section 24 is, forexample, a rectangle in a direction parallel to the glass substrate 1,and one side of the rectangle is fixed to 1 mm. The graph of FIG. 4shows the required mean distribution volume of the conductive particles20 when the width of the transfer section, i.e., the area of therectangle is varied.

As shown in the Figure, in the case of a liquid crystal panel having thetransfer section 24 of 100 μm wide, the required volume of theconductive particles 20 is not less than 300/mm² in passive driving. Onthe other hand, the volume is not less than 60/mm² is only sufficient inactive driving. Similarly, when the width of the transfer section 24 is60 μm, the required volume of the conductive particles is not less than500/mm² in passive driving, as opposed to not less than 100/mm² which isonly sufficient in active driving. Further, when the width of thetransfer section 24 is 30 μm, the required volume of the conductiveparticles 20 is not less than 1000/mm² in passive driving, as opposed tonot less than 200/mm² which is only sufficient in active driving.

Further, Table 2 and FIG. 22 show a correlation between the averagenumber of the conductive particles 20 in the transfer section 24 andoccurrence of defect liquid crystal panels when the distribution volumeof the conductive particles 20 is varied.

TABLE 2 NUMBER OF CONDUCTIVE NUMBER OF PARTICLE DEFECTS JUDGEMENT 3 5/5 x 4 3/35  x 5 0/355 ∘ . . . . . . . . . 10  0/329 ∘ * ∘ = acceptable forcommercial production x = unacceptable for commercial production

The table shows the result of an evaluation on average numbers ofconductive particles when the mean distribution volume is varied andoccurrence of lighting failures caused by transfer failure in a panelwhich was created for each different average number of conductiveparticles when transfer pad area S is 0.025 mm². Here, “transferfailure” refers to the case where there are no conductive particles 20in the transfer section 24 so that electrical conduction fails, and thecase where a deficiency such non-uniform display or the like is causedby a resistance variation even in the presence of the conductiveparticles 20. Note that, the evaluation was made under lightingconditions, and the panels used for the evaluation had 660 wires.

When the average number of the conductive particles 20 in the transfersection 24 was about three, all of the panels used for the evaluationhad transfer points having no conductive particles 20, and showedtransfer failure. Further, when the average number of the conductiveparticles 20 in the transfer section 24 was about four, three inthirty-five panels used for the evaluation showed transfer failure whichis about 10% of the total. The transfer failure in this case was alsocaused by the absence of the conductive particles 20 in the transfersection 24.

On the other hand, when the average number of the conductive particles20 in the transfer section 24 was about five, among three hundred fiftyfive panels evaluated, none of these panels showed transfer failurecaused by the absence of the conductive particles 20 in the transfersection 24, or transfer failure due to non-uniform display which occurseven in the presence of the conductive particles 20. Likewise, when theaverage number of the conductive particles 20 in the transfer section 24was about ten, among three hundred twenty-nine panels evaluated, none ofthese panels showed transfer failure.

Further, when the average number of the conductive particles 20 in thetransfer section 24 was about five, there were no failures such asnon-uniform display or the like which are caused by transfer of theconductive particles 20, even though some transfer points were foundhaving only one conductive particles 20 were found. Thus, this resultshows that a sufficient resistance can be provided when the transfersection 24 has at least one conductive particles 20.

Considering the transfer section 24 in view of these results, bydetermining and distributing distribution volume of the conductiveparticles 20 which is required to provide five particles in the transfersection 24 on average, the occurrence of failures can be suppressedalmost completely to make it available for commercial production.

Namely, assuming that the mean distribution volume of the conductiveparticles 20 is D (piece)/mm², and the area of the transfer section 24is S mm², it can be seen that the occurrence of failures can besuppressed almost completely when the distribution volume D (piece) ofthe conductive particles 20 is not less than 5/S.

Here, in the case where the mean distribution volume of the conductiveparticles 20 is too large, there arises problems such as a decrease ofadhesion in the sealing section 3, uneven thickness of the cell, and anincrease of leakage between the wires caused by aggregation of theconductive particles 20. Table 3 shows a relation between the meandistribution volume of the conductive particles 20 and occurrence offailures. Note that, in Table 3, the gap between wires (the distancebetween adjacent transfer sections 24) is 15 μm.

TABLE 3 MEAN DISTRIBUTION LEAKAGE CELL VOLUME BETWEEN WIRES ADHESIONTHICKNESS 1600 x x x 1400 x x x 1200 x Δ x 1000 ∘ Δ Δ  800 ∘ Δ Δ  600 ∘∘ Δ  400 ∘ ∘ ∘  200 ∘ ∘ ∘

As shown in Table 3, when the mean distribution volume conductiveparticles 20 is 1200 (piece)/mm², the probability of leakage betweenwires is about 1%. On the other hand, when the mean distribution volumeof the conductive particles 20 is 1000 (piece)/mm², the probability ofleakage between wires does not exceed 1%, which poses no problem forcommercial production of the liquid crystal display device. Further,when the mean distribution volume of the conductive particles 20 isfurther reduced, it is clearly understood that the probability ofleakage between wires is also further lowered.

In a relation between the mean distribution volume of the conductiveparticles 20 and adhesion, the adhesion should be stronger than glassstrength. More specifically, as shown in FIG. 5, when performing apressure test which applies pressure on the portion indicated by thearrow after affixing the glass substrate 1 and the counter substrate 2to find the pressure value which separates the two substrates, or breaksthe glass substrate 1, it is preferable that the adhesion is firm enoughto break the glass substrate 1 before the two substrates are separatedat the sealing section 3.

If the adhesion is such that it is weaker than the glass strength, andcauses separation of the two substrates in a cutting process or achamfer process and the like which are necessary for creating the liquidcrystal panel, it is difficult to create the liquid crystal panel with adesirable yield. This level of adhesion is denoted by × in the columnsunder ADHESION in Table 3. Meanwhile, if the two substrates stay joinedin the foregoing manufacturing processes, it is possible to create theliquid crystal panel without lowering the yield. However, if the productliquid crystal panel fails, for example, the impact-strength test, it isnecessary to reinforce the adhesion of the panel with silicon resin.This is not preferable because it increases the manufacturing cost. Itis therefore preferable that the adhesion is stronger than the glassstrength. In Table 3, the case where the adhesion is stronger than theglass strength is denoted by o, and the case where the adhesion isstrong enough to create the liquid crystal panel but weaker than theglass strength is denoted by Δ.

As shown in Table 3, when the mean distribution volume of the conductiveparticles 20 is not more than 600 (piece)/mm², adhesion of the sealingsection 3 is stronger than the glass strength. On the other hand, whenthe mean distribution volume of the conductive particles 20 is not lessthan 1400 (piece) /mm², the adhesion is weak enough to cause separationof the two substrates in the cutting process or the chamfer process andthe like which are necessary after the glass substrate 1 and the countersubstrate 2 have been combined. Further, when the mean distributionvolume of the conductive particles 20 is 800 (piece)/mm² to 1200(piece)/mm², adhesion of the sealing section 3 is weaker than glassstrength but is strong enough to prevent separation in the cuttingprocess or the chamfer process.

Further, as for evenness of the cell thickness, the following considersthe case where the finished thickness of the cell is 4.5 μm for example,if the cell thickness has a variation of ±0.3 μm or greater, flicker islikely to occur since it is difficult to precisely join the glasssubstrate 1 and the counter substrate 2 because of unevenness of liquidcrystal capacities. Further, if the cell thickness has a variation of±0.5 μm or greater, the difference of the cell thickness becomesdifference of transmittance which is perceived as non-uniform display.

Thus, in the evaluation of Table 3, the case where the absolute value ofthe variation of the cell thickness is not less than 0.5 μm is denotedby ×, the case where the absolute value of the variation of the cellthickness is more than 0.3 μm but less than 0.5 μm is denoted by Δ, andthe case where the absolute value of the variation of the cell thicknessis not more than 0.3 μm is denoted by o.

As shown in Table 3, it is possible to keep the cell thickness even whenthe mean distribution volume of the conductive particles 20 is not morethan 400 (piece)/mm². However, when the mean distribution volume of theconductive particles 20 is not less than 1200 (piece)/mm², it is notpossible to keep the cell thickness even and non-uniform display occurs.

As described, considering to those three factors: leakage between wires;adhesion of the substrates; and cell thickness, it is desirable that themean distribution volume of the conductive particles 20 is not more than1000 (piece)/mm². More preferably, the mean distribution volume of theconductive particles 20 is not more than 600 (piece)/mm², and furtherpreferably, it is not more than 400 (piece)/mm².

Also, assuming that the mean distribution volume of the conductiveparticles 20 is D (piece) /mm², and the area of the transfer section 24is S mm², the transfer section 24 performs stable transfer when the meandistribution volume of the conductive particles 20 D is within a rangeof the following inequality (1).

D>5/S  (1)

Namely, it is possible to maintain high reliability of the liquidcrystal display device without decreasing liquid crystal retentivity inthe vicinity of the sealing section 3 even under the conditions of hightemperature and high humidity. Namely, taking into consideration of theresult shown in Table 3, when the mean distribution volume of theconductive particles 20 D is within a range of the following inequality(2),

1000≧D>5/S  (2),

it is possible to prevent inadequate adhesion at the sealing section 3,uneven cell thickness, and an increase of occurrence of leakage betweenwires which is caused by aggregation of the conductive particles 20, andthereby prevent reliability of the liquid crystal display device frombecoming poor, even under the conditions of high temperature and highhumidity.

Therefore, it is possible to obtain a high-precise liquid crystal panelwith desirable yield, and a narrow pitch. Further, it becomes possibleto provide a liquid crystal display device at lower cost since activedriving requires less volume of the conductive particles 20 than that ofpassive driving.

Note that, the lower contact pads 12 may be made of ITO as with theupper contact pads 16. The lower contact pads 12 and the upper contactpads 16 may be both made of Ta, or, may be made of ITO with differentdegrees of oxidation as long as the lower contact pads 12 havesubstantially the same resistance as that of the upper contact pads 16.For example, FIG. 7 shows the arrangement in which the lower contactpads 12 and the upper contact pads 16 are both made of ITO. Further,FIG. 8(a) shows the arrangement of the transfer section 24 in this case.

As shown in FIG. 7, the input terminals 15 a made of Ta and the lowercontact pads 12 made of ITO are electrically connected by partiallyoverlapping each other. The upper contact pads 16 and the gradationsignal lines 15, both made of ITO, are electrically connected to eachother. The lower contact pads 12 and the upper contact pads 16 areelectrically connected to each other via the conductive particles 20.

In order to manufacture the liquid crystal display device having thearrangement shown in FIG. 7, in the described manufacturing process ofthe liquid crystal display device shown in FIGS. 1(a) through 1(e), thepatterning of the lower contact pads 12 should be performed whenpatterning the drain electrodes 6, the pixel electrodes 9 and the likeafter the silicon nitride film 8 has been deposited, instead ofperforming it when patterning the scanning lines 5. This provides thelower contact pads 12.

Since the conductive particles 20 are distributed at random in thesealing section 3, the upper contact pads 16 and the lower contact pads12 are connected to each other via the conductive particles 20 either inthe vicinity of the edge of the glass substrate 1 or at a portiondistanced from the edge of the glass substrate 1. When the transfersection 24 has the arrangement shown in FIG. 2(a), the former case isshown in FIG. 2(b), and the latter case is shown in FIG. 2(c).

In the arrangement shown in FIG. 2(a), the gradation signal lines 15 andthe upper contact pads 16 are made of ITO. On the other hand, the inputterminals 15 a of the gradation signal lines 15 and the lower contactpads 12 are lade of Ta, which has a smaller resistance than that of ITO.Therefore, R_(D-D′), which is the resistance between D-D′ (see FIG.2(c)) is smaller than R_(C-C′), which is the resistance between C-C′(see FIG. 2(b)), because the former includes more Ta. Namely,R_(C-C′)>R_(D-D′). Thus, if adjacent transfer sections 24 have differentdistributions of the conductive particles 20, the effective value of thesignal voltage becomes different due to a delay of the signal voltage ofthe gradation signal lines 15, this causes non-uniform display on eachgradation signal line 15.

On the other hand, in the arrangement shown in FIG. 8(a), in otherwords, in the case where the lower contact pads 12 are made of ITO aswith the upper contact pads 16, R_(G-G′) which is the resistance betweenG-G′ (see FIG. 8(b)), and R_(H-H′), which is the resistance between H-H′(see FIG. 8(c)), are substantially the same.

This makes it possible to suppress the variation of contact resistancebetween the lower contact pads 12 and the upper contact pads 16 causedby a variation of distribution of the conductive particles 20 in thesealing section 3, thereby providing a liquid crystal display device ofa desirable display quality which can suppress non-uniform display.

Note that, as shown in FIG. 2(d), in the case where the transfer section24 has the staggered arrangement, R_(F-F′), which is the resistancebetween F-F′ (see FIG. 2(f)), is smaller than R_(E-E′), which is theresistance between E-E′ (see FIG. 2(e)), as with the case shown in FIG.2(a), because the former includes more Ta. Namely, R_(E-E′)>R_(F-F′).Thus, the conductive particles 20 are differently distributed inadjacent transfer sections 24, and non-uniform display occurs on eachgradation signal line 15.

On the other hand, in the arrangement shown in FIG. 8(d), since thelower contact pads 12 are made of ITO as with the upper contact pads 16,R_(I-I′), which is the resistance between I-I′ (see FIG. 8(e)), andR_(J-J′), which is the resistance between J-J′ (see FIG. 8(f)), aresubstantially the same despite the variation of distribution of theconductive particles 20. Therefore, it is possible to suppress thevariation of contact resistance between the lower contact pads 12 andthe upper contact pads 16 in adjacent transfer sections 24.

Further, as shown in FIGS. 9(a) and 9(c), an insulation film 25 with anopening 25 a (opening section) may be provided on the glass substrate 1in the sealing section 3, and the lower contact pads 12 may be disposedin the opening 25 a. FIG. 9(a) shows the same arrangement as that ofFIG. 1(a) but includes the insulation films 25. The glass substrate 1 ofFIG. 9(a) and the counter substrate 2 of FIG. 1(b) are combined togetherto have the arrangement of FIG. 9(b).

The insulation film 25 is provided by forming a silicon nitride filmover the input terminals 5 a, 10 a, 15 a beneath the sealing section 3,and then removing only a portion of the silicon nitride film whichcovers the lower contact pads 12, so as to form the opening 25 a.

By the lower contact pad 12 which is exposed at the opening 25 a, theupper contact pad 16 and the lower contact pad 12 are electricallyconnected to each other via the conductive particles 20 which aredistributed in the opening 25 a.

Consequently, as shown in FIGS. 9(c) and 9(d), the upper contact pads 16and the lower contact pads 12 are electrically connected to each otheronly via the conductive particles 20 which are distributed in theopening 25 a, thereby suppressing leakage between wires in adjacenttransfer sections 24 even when the conductive particles 20 aggregate.

In the case where the insulation film 25 is not provided, in the areawhich is not required to be electrically connected via the conductiveparticles 20, it is necessary to provide a gap greater than the diameterof the conductive particles 20 (for example, 7 μm) between wires, so asto avoid leakage between wires such as the input terminals 15 a, whichare routing wiring section of the gradation signal lines 15.

However, by forming the insulation film 25 in the area which is notrequired to be electrically connected via the conductive particles 20,it becomes possible to reduce the gap between wires to the diameter ofthe conductive particles 20 or smaller. This makes it possible to alsoreduce the routing wiring section of the input terminals 15 a, therebyrealizing a liquid crystal display device having a smaller frame withoutinducing leakage between wires via the conductive particles 20.

Further, in the case where the insulation film 25 is formed, as shown inFIG. 9(c), the gap between the glass substrate 1 and the countersubstrate 2 is determined by the thickness d3 of the insulation film 25and the diameter d2 of the spacers 21. Further, the conductive particles20 electrically connect the upper contact pad 16 and the lower contactpad 12 by being slightly deformed in the opening 25 a of the insulationfilm 25.

Here, it is preferable that the diameter d1 of the conductive particles20 is greater than the gap between the glass substrate 1 and the countersubstrate 2 (the cell thickness), in other words, the sum of thethickness d3 of the insulation film 25 (the thickest portion of the filmin the sealing section 3) and the diameter d2 of the spacers 21(d1>d2+d3). According to this diameter d1, the two substrates 1 and 2are combined by curing the sealing material while applying pressure toslightly deform the conductive particles 20. Thus, by deforming theconductive particles 20, it is possible to maintain the electricalconnection even when the cell thickness: the gap between the glasssubstrate 1 and the counter substrate 2, varies or changes. This enablesa stable electrical connection, and provides stability against thevariations or changes of the cell thickness.

Note that, as shown in FIG. 11, in the arrangement having the insulationfilm 25, the lower contact pads 12 and the upper contact pads 16 may beboth made of ITO as with the arrangement shown in FIG. 7. As shown inFIG. 11, the input terminals 15 a of the gradation signal lines 15 madeof Ta, and the lower contact pads 12 made of ITO are electricallyconnected to each other by partially overlapping each other. FIG. 10(a)shows the arrangement of the transfer section 24 in this case.

In the arrangement shown in FIG. 10(a), R_(M-M′), which is theresistance between M-M′ (see FIG. 10(b)), and R_(N-N′), which is theresistance between N-N′ (see FIG. 10(c)), are substantially the same aswith the arrangement shown in FIG. 8(a).

This makes it possible to suppress the variation of contact resistancebetween the lower contact pads 12 and the upper contact pads 16 causedby a variation of distribution of the conductive particles 20 in thesealing section 3.

Further, as shown in FIG. 10(d), in the case where the transfer section24 has the staggered arrangement, R_(O-O′), which is the resistancebetween O-O′ (see FIG. 10(e)) and R_(P-P′), which is the resistancebetween P-P′ (see FIG. 10(f)), are substantially the same as with thearrangement shown in FIG. 8(b). This makes it possible to preventleakage between adjacent transfer sections 24, and also, makes itpossible to increase the area of the transfer section 24, therebyreducing the contact resistance in the transfer section 24. As a result,the required area for the upper contact pad 16 or lower contact pad 12can be reduced, and display failure due to blunting of the signalvoltage can be prevented, thereby providing a high-precision liquidcrystal display device.

Note that, the input terminals 5 a, 10 a and 15 a are not necessarilyrequired to be formed on the glass substrate 1 which bears the TFTs 11as long as they all are formed on a single substrate. Alternatively,these input terminals may be formed on the counter substrate 2.

Further, the insulation film 25 having the opening 25 a is notnecessarily required to be formed on the glass substrate 1 as long asthe upper contact pads 16 and the lower contact pads 12 are connectedvia the opening 25 a. Alternatively, the insulation film 25 may beformed on the counter substrate 2 or on both of the glass substrate 1and the counter substrate 2.

[Second Embodiment]

The following will explain another embodiment of the present inventionwith reference to FIGS. 13(a) through 13(e) and FIGS. 14(a) through14(d). For ease of explanation, components having the equivalentfunctions to those shown in the drawings pertaining to the firstembodiment will be given the same reference symbols, and explanationthereof will be omitted here.

As shown in FIG. 13(e), as with the First embodiment, a liquid crystaldisplay device according to the present embodiment has a glass substrate1 made of glass and a counter substrate 2 which are opposed via asealing section 3. And these two substrates are sealed with a liquidcrystal layer 4 (medium layer).

Further, on the glass substrate 1 which is an active matrix substrate, aTFT 34, a pixel electrode 9, a gradation signal line 35, an inputterminal 30 a of a reference signal line 30 and a lower contact pad 12are disposed. Note that, the TFT 34 includes a scanning line 5 (thefirst signal wiring), a drain electrode 6, a source electrode 33 and asilicon nitride film 8.

Pixel electrodes 9 are disposed in a matrix manner. And a TFT 34 whichis a switching element having three terminals is provided on each pixelelectrode 9.

In each of the TFTs 34, the drain electrode 6 is connected to the pixelelectrode 9, and the source electrode 33 is connected to a samegradation signal line 35 in each of the TFTs 34 which are horizontally(in a column direction) aligned in a display screen.

The silicon nitride film 8 which is formed on substantially the entiresurface of the glass substrate 1 while covering the scanning lines 5 isa gate insulation film. The lower contact pads 12 and the pixelelectrode 9 are made of transparent conductive film such as ITO (IndiumTin Oxide).

As shown in FIG. 13(c), the scanning lines 5 are disposed in parallelwith reference signal lines 30 (the second signal wiring, describedlater), and an input terminal 5 a of the scanning line 5 and an inputterminal 30 a of the reference signal line 30 are connected to a drivingIC 31.

The gradation signal lines 35 are data lines to which a data signal isprovided, and are orthogonally disposed to the scanning lines 5 on theglass substrate 1 as shown in FIG. 13(a). The input terminal 35 a of thegradation signal line 35 is connected to a driving IC 32.

Further, the lower contact pads 12 are connected to the input terminals30 a of the reference signal lines 30 (described later) which areconnected to the driving IC 31. Here, the input terminals 30 a of thereference signal lines 30 also act as routing wiring of the referencesignal lines 30.

The scanning line 5, the input terminal 5 a, the source electrode 33,the drain electrode 6, the input terminal 30 a, the gradation signalline 35 and the input terminal 35 a are formed by metal such as Ta,respectively.

Meanwhile, as shown in FIG. 13(e), an overcoat film 19 is formed on thecounter substrate 2 so as to cover a color filter 18. Further, thereference signal lines 30, upper contact pads 16 and a counter electrode17 are provided on the overcoat film 19.

The reference signal lines 30 are signal wiring which applies voltage tothe liquid crystal layer 4, and are disposed in parallel with thescanning lines 5 on the glass substrate 1. In this arrangement, as shownin FIG. 13(b) and 13(e), each reference signal line 30 also act as thecounter electrode 17 at the portion opposite to the pixel electrode 9,and also, act as the upper contact pads 16 at the portion opposite tothe lower contact pads 12. Namely, the counter electrode 17 and theupper contact pads 16 are connected to the reference signal lines 30.The reference signal lines 30 is made of transparent conductive filmsuch as ITO.

As shown in FIG. 13(d), the upper contact pads 16 is connected to thelower contact pads 12 via the conductive particles 20. Namely, thereference signal line 30 transfers to the glass substrate 1 via thetransfer section 24.

The following will explain a driving principle of liquid crystal.

The liquid crystal display device sequentially scans timeshared displaydata along the scanning lines 5 to display a screen.

For example, when a scanning line 5 is horizontally scanned, a gatevoltage for turning on the TFT 34 is applied to the scanning lines 5.Meanwhile, a gate voltage for turning off the TFT 34 is applied to theother scanning line 5. Thus, when the scanning line 5 is horizontallyscanned, only the TFT 34 belonging to the scanned scanning line 5 turnson, and a signal voltage which was applied to the gradation signal line35 passes from the source electrode 33 to the drain electrode 6, andthen, is applied to the pixel electrode 9 of the scanning line 5. Withthese processes, the liquid crystal on each pixel electrode 9 is drivenby the potential difference between the pixel voltage applied to thepixel electrode 9, and a counter voltage applied to the counterelectrode 17.

As described, by sequentially scanning the scanning line 5 and applyingthe signal voltage in accordance with driving condition of each pixel toall of the gradation signal lines 35, it is possible to display all ofthe required pixel.

The following will explain an example of the manufacturing processes ofthe glass substrate 1 used for the liquid crystal display device, shownin FIGS. 13(a) through 13(e) according to the present embodiment. Notethat, the manufacturing processes of the counter substrate 2 and themounting process refer to that of the First Embodiment.

Firstly, a metal film made of Ta or the like is deposited on a glasssubstrate 1 by a sputtering method. And then, a scanning line 5, aninput terminal 5 a of the scanning line 5, an input terminal 30 a of thereference signal line, an input terminal 35 a of the gradation signalline 35 are formed by patterning the metal film into desired shape usinga photo-lithography method. The input terminals 5 a, 30 a and 35 arespectively include routing wiring sections, and connecting sections ofdriving circuits such as the driving ICs 31 and 32. And the connectingsections for driving circuits include electrodes (not shown) forreceiving an external signal voltage. Here, the arrangement of the inputterminals adopted in the present embodiment is for a liquid crystaldisplay element having the COG structure; however, the input terminals 5a, 30 a and 35 a may have electrodes for being connected to a TAB sothat a liquid crystal display element equipped with the TAB can berealized.

Next, a silicon nitride film 8 is deposited on substantially the entireof the glass substrate 1 so as to cover the scanning lines 5 by theplasma CVD (Chemical Vapor Deposition). Thereafter, the patterning iscarried out by the photo-lithography method such that the siliconnitride film 8 which is formed on the area where the input terminals 5a, the input terminals 30 a and the input terminals 35 a will be formed.Next, an intrinsic semiconductor layer and an active semiconductor layerare continuously deposited using plasma CVD. And then, the intrinsicsemiconductor layer and the active semiconductor layer are patternedinto land shapes. During the patterning, the part (channel section) ofthe active semiconductor layer which is formed between the sourceelectrode 33 and the drain electrode 6 is removed.

Next, after preparing a metal film made of Ta is deposited by thesputtering method, the source electrode 33, the drain electrode 6 andthe gradation signal line 35 are formed by patterning the metal filminto a desirable form using the photo-lithography method. And, afterdepositing an ITO film which is a transparent conductive film by asputtering method, the pixel electrodes 9 and the lower contact pads 12are formed by patterning the ITO film using the photo-lithographymethod. Here, the drain electrode 6 and the pixel electrode 9 areelectrically connected.

Next, the silicon nitride film is formed on substantially the entiresurface of the glass substrate 1 by the plasma CVD, and then ispatterned by the photo-lithography method so as to remove the area wherethe input terminals 5 a, the input terminals 30 a, the input terminals35 a will be formed and to form a protection film (not shown).

Further, an alignment film (not shown) is formed by the printing, and isaligned by rubbing.

Meanwhile, on the counter substrate 2, after depositing an ITO filmwhich is a transparent conductive film by the sputtering method, thecounter electrode 17, the reference signal line 30 and the upper contactpads 16 are formed by patterning the ITO film into desirable form usinga photo-lithography method. Here, the counter electrode 17, thereference signal line 30 and the upper contact pads 16 are formed into acontinuous pattern to be electrically conductive each other. Note that,a substrate having a color filter layer 18 and an overcoat film 19 isused as the counter substrate 2.

Further, after forming an alignment film (not shown) by printing, thealignment film is aligned by rubbing.

The process of combining the glass substrate 1 and the counter substrate2, and the rest of the processing are the same as those of the firstembodiment.

Note that, as shown in FIGS. 14(a) through 14(d), an insulation film 40may be formed on the silicon nitride film 8 so that the lower contactpads 12 expose. The insulation film 40 has an opening 40 a to expose thelower contact pads 12. The insulation film is made of silicon nitridefor example.

Therefore, it is possible to electrically connect the lower contact pads12 and the upper contact pads 16 only via the conductive particles 20which are distributed in the opening 40 a as with the liquid crystaldisplay device shown in FIGS. 9(a) through 9(d). By thus forming theinsulation film 40 on the area not required to be electrically connectedvia the conductive particles 20, it is possible to reduce the gapbetween the wires smaller than the diameter of the conductive particles20. This also makes it possible to reduce the routing wiring section inthe input terminals 30 a, thereby realizing a liquid crystal displaydevice having a smaller frame without inducing leakage between the wiresvia the conductive particles 20. Further, it is possible to suppressleakage between wires in the adjacent transfer sections 24 even when theconductive particles 20 aggregate.

[Third Embodiment]

The following will explain the third embodiment of the present inventionwith reference to FIGS. 15(a) through 15(e) and FIG. 16. For ease ofexplanation, components having the equivalent functions to those shownin the drawings pertaining to the first embodiment will be given thesame reference symbols, and explanation thereof will be omitted here.

A liquid crystal display device shown in FIGS. 15(a) through 15(e) hasan arrangement using MIM (metal insulator metal) 55 which is an elementhaving two terminals, as a switching element. As shown in FIG. 15(e),the liquid crystal display device according to the present embodimentincludes the MIM (switching element) 55 having a segment line 52 (firstsignal wiring) and a counter electrode metal 56, a pixel electrode 9, acommon line 51 and a lower contact pad 12 (a first contact pads) whichare provided on a glass substrate 1.

The MIM 55 is controlled so as to turns on/off in accordance with thepotential difference between the segment line 52 as a scanning line, andthe common line 51 as a signal line. When the MIM 55 is on, potential ofnot less than a subthreshold value is applied to the MIM 55 so that theresistance of the MIM 55 is reduced and charges are injected into theliquid crystal layer 4. Thus, the liquid crystal layer is driven.

As shown in FIG. 15(a), the lower contact pads 12 is connected to aninput terminal 51 a of the common line 51 (described later) which isconnected to a driving IC 53 (see FIG. 15(c)).

Further, the segment line 52, an input terminal 52 a of the segment line52, the input terminal 51 a of the common line 51 and the lower contactpads 12 are made of Ta, and the pixel electrode 9 is made of ITO.

Meanwhile, as shown in FIG. 15(e), an overcoat film 19 is formed on thecounter substrate 2 so as to cover a color filter layer 18. The commonline 51 (the second signal wiring), the upper contact pads 16 (thesecond contact pads) and the counter electrode 17 are provided on theovercoat film 19.

The common lines 51 are orthogonally disposed to the segment lines 52 onthe glass substrate 1. In this arrangement, as shown in FIG. 15(b), eachcommon line 51 also acts as the counter electrode 17 at the portionopposite to the pixel electrode 9, and also, acts as the upper contactpad 16 at the portion opposite to the lower contact pad 12.

The common lines 51 and the upper contact pads 16 are made of atransparent conductive film such as ITO. Here, the input terminals 51 aalso act as routing wiring of the common lines 51.

Further, as shown in FIG. 15(a), a sealing section 3 for sealing theliquid crystal of the liquid crystal layer 4 is provided while enclosingthe display area 29 which is placed between the glass substrate 1 andthe counter substrate 2. The sealing section 3 is made of a sealingmaterial of ultraviolet setting resin as with the first embodiment, andhas spacers 21 and conductive particles 20. Further, as shown in FIG.15(d), a transfer section 24 is formed in an overlapping area of theconductive particles 20, the lower contact pads 12 and the upper contactpads 16.

As described, since the input terminals 51 a and 52 a are both formed onthe glass substrate 1, it is possible to mount the TAB etc. to a liquidcrystal panel without turning over the liquid crystal display element.This increases the efficiency of the mounting, thereby reducingmanufacturing cost.

Further, since the input terminal 51 a which also act as the routingwiring of the common line 51 is made of a material of smaller resistance(for example, Ta) than that of the material of the common line 51 (forexample, ITO), it is possible to narrow a line width of the inputterminal 51 a, i.e., a wiring pitch and create a COG structure with asmall pitch. Further, it is also possible to reduce the frame area(non-display area) of a liquid crystal display element.

Further, it is possible to form the input terminals 51 a on the glasssubstrate 1 made of glass (on a surface of the glass, or on an inorganicfilm deposited on the substrate 1) instead of forming the input terminal51 a on the overcoat film 19 made of resin and formed on the countersubstrate 2. This improves the mechanical strength and the adhesionbetween the input terminals 51 a and the glass substrate 1, and alsoprotects the terminal part from breakage when handling. Also, this makesre-work of mounting easier in case of mounting of the TAB, etc. isfailed, thereby improving the yield.

The following will explain an example of the manufacturing steps of theglass substrate 1 used for the liquid crystal display device accordingto the present embodiment. Note that, the manufacturing processes of thecounter substrate 2 refers to those of the First Embodiment.

Firstly, a metal film of Ta or the like is deposited on a glasssubstrate 1 by the sputtering method. And then, the segment line 52, aninput terminal 52 a of the segment line 52, an input terminal 51 a ofthe common line 51, and the lower contact pads 12 are formed bypatterning into a desirable form using photo-lithography. At this point,the input terminals 51 a and 52 a respectively include routing wiringsections, and connecting sections of driving circuits. And theconnecting sections for driving circuits includes electrodes (not shown)for receiving an external signal voltage. Here, the arrangement of theinput terminals adopted in the present embodiment is for a liquidcrystal display element of the COG structure; however, the inputterminals 51 a and 52 a may have electrodes for being connected to a TABso that a liquid crystal display element equipped with the TAB can berealized.

Next, an oxide film of Ta₂O₅ is formed as an active layer using ananodic oxidization method. And then, the oxide film of Ta₂O₅ on theinput terminals 51 a and 52 a is removed by a photo-lithography methodor an etching method.

Then, Cr film is deposited by the sputtering method, and the counterelectrode metal 56 of MIM 55 is formed into land shapes by thephoto-lithography method.

And thereafter, an ITO film is formed by the sputtering method, and thepixel electrode 9 is formed by a photo-lithography method. Note that,the pixel electrode 9 is electrically connected to the counter electrodemetal 56.

Further, an alignment film (not shown) is formed by printing, and isaligned by rubbing.

Note that, as shown in FIG. 16, the lower contact pads 12 and the uppercontact pads 16 can be both made of ITO. At this point, the inputterminals 51 a made of Ta, and the lower contact pads 12 made of ITO areelectrically connected by partially overlapping each other.

This makes it possible to suppress the variation of contact resistancebetween the lower contact pads 12 and the upper contact pads 16, thevariation being caused by the variation of the conductive particles 20in the sealing section 3, thereby suppressing non-uniform display. Thisensures to provide a liquid crystal display of desirable displayquality.

As described, the liquid crystal display devices in those embodimentsinclude a substrate having switching element and a counter substratewhich are opposed and sealed with liquid crystal of a liquid crystallayer. The first signal wiring for controlling the switching element isprovided on one of these substrates, and the second signal wiring whichis opposite to the first signal wiring and applies voltage to the liquidcrystal layer is provided on the other substrate. In the liquid crystaldisplay device having a sealing section for sealing liquid crystal of aliquid crystal layer while enclosing the display area between twosubstrates, the sealing section may have conductive particles in itstransfer section to electrically connect the first signal wiring or thesecond signal wiring, to the substrate opposite to the first signalwiring or the second signal wiring.

With this arrangement, in a liquid crystal display device of activedriving, the first signal wiring or the second signal wiring iselectrically connected to the substrate opposite to the first signalwiring or the second signal wiring via the conductive particle. Namely,the first signal wiring is electrically connected to the substrateopposite to the first signal wiring, or the second signal wiring iselectrically connected to the substrate opposite to the second signalwiring. Generally, active driving has wider permitted limit for thevariation of contact resistance than that of passive driving. Thus, itrequires less volume of the conductive particle, thereby making itpossible to provide a liquid crystal display device of lower-cost.

In the foregoing liquid crystal display, it is preferable that an inputterminal of the first signal wiring and an input terminal of the secondsignal wiring are provided on one of those substrates (the substratehaving the switching element and the counter substrate).

With the arrangement, it is possible to mount a driving IC which isconnected to the input terminals of the first signal wiring, and adriving IC which is connected to the input terminals of the secondsignal wiring on a single substrate. Therefore, it is not necessary toturn over the liquid crystal display element during the mounting processof a TAB on a liquid crystal panel. This increases the efficiency ofmounting, thereby reducing manufacturing cost. Further, the driving ICcan be provided as a single chip. Accordingly, the mounting can be morecompact in size, and the cost of the element required for the driving ICand manufacturing cost can be reduced.

In the foregoing liquid crystal display device, it is preferable thatthe transfer section is provided on a first substrate which is one ofthose substrates bearing the input terminal of the first signal wiringand the input terminal of the second signal wiring. The transfer sectionis made up of the first contact pads connected to either of the firstsignal wiring or the second signal wiring which are provided on thefirst substrate, and the second contact pads connected to either of thefirst signal wiring or the second signal wiring which are provided onthe second substrate, and the conductive particles connected to thefirst contact pads and the second contact pads.

With the foregoing arrangement, it is possible to electrically connectthe first signal wiring and the substrate opposite to the first signalwiring, or the second signal wiring and the substrate opposite to thesecond signal wiring via the conductive particle, the first contactpads, and the second contact pads. Therefore, it is not necessary toturn over the liquid crystal display element during the mounting processof a TAB on a liquid crystal panel. This increases the efficiency ofmounting, thereby reducing manufacturing cost.

In the foregoing liquid crystal display device, it is preferable thatresistance of the first contact pads and the second contact pads aresubstantially the same.

With the foregoing arrangement, it is possible to suppress the variationof contact resistance between the first contact pads and the secondcontact pads caused by variation of distribution of the conductiveparticles in the sealing section. This suppresses occurrence ofnon-uniform display, thereby providing a liquid crystal display ofdesirable display quality.

In the foregoing liquid crystal display device, it is preferable thatthe transfer section is provided between the first signal wiring and thefirst signal generation circuit which provides signal to the firstsignal wiring, or between the second signal wiring and the second signalgeneration circuit which provides signal to the second signal wiring.

With the foregoing arrangement, it is possible to downsize the routingwiring section of the first signal wiring or the second signal wiring,thereby reducing the frame area (non-display area) in the liquid crystaldisplay device. Thus, it is possible to realize a liquid crystal displaydevice with a smaller frame.

In the foregoing liquid crystal display device, when assuming that themean distribution volume of the conductive particles is D (piece) /mm²,and the area of the transfer section horizontal to the substrates is Smm², it is preferable that the mean distribution volume of theconductive particles 20 should satisfies 1000≧D>5/S. To be moredesirable, the mean distribution volume of the conductive particles 20satisfies 600≧D>5/S. To be further desirable, it satisfies 400≧D>5/S.

With the foregoing arrangement, it is possible to prevent an increase ofleakage between the wires due to a decrease of adhesion of the sealingsection, uneven thickness of the cell, and aggregation of the conductiveparticles, thereby preventing reliability of the liquid crystal displaydevice from becoming poor, even under the conditions of high temperatureand high humidity. Accordingly, it is possible to produce a liquidcrystal panel with desirable yield, high precision and a small pitch,thereby providing a liquid crystal display device with high reliability.

In the foregoing liquid crystal display device, it is preferable thatthe first substrate is the substrate having the switching element.

With the foregoing arrangement, the input terminal of the first signalwiring and the input terminal of the second signal wiring are providedon the substrate having the switching element. This makes it possible toform the input terminal of the first signal wiring and the inputterminal of the second signal wiring on a glass (the material of thesubstrate having the switching elements) or an inorganic film formed onthe substrate having the switching elements without extra manufacturingsteps. Therefore, the strength can be improved since the input terminalof the first signal wiring and the input terminal of the second signalwiring have desirable adhesion.

Further, the substrate having the switching elements necessarily hasmetal wiring of small resistance. Meanwhile, wiring made by asingle-layer transparent conductive film of ITO or the like is formed onthe counter substrate which also acts as pixel electrode. Generally, thetransparent conductive film of ITO or the like has greater resistancethan metal wiring of Ta or AI or the like since transmittance is itsimportant factor. Thus, a wider wiring pitch is required when routingwiring.

However, providing the input terminal of the first signal wiring and theinput terminal of the second signal wiring on the substrate having theswitching element realizes routing wiring of low resistance, therebynarrowing the frame and making the mounting compact in size.

In the foregoing liquid crystal display device, it is preferable thatthe input terminal of the first signal wiring and the input terminal ofthe second signal wiring are made of a conductive material of smallerresistance than that of the first signal wiring and the second signalwiring formed on the second substrate.

With the foregoing structure, it is possible to narrow the width of theinput terminal of the first signal wiring and the input terminal of thesecond signal wiring, in other words, narrow the wiring pitch, therebyensuring to create a COG structure with a small pitch. Further, thisensures a liquid crystal display device with a smaller frame, therebymaking the mounting compact in size, and reducing the mounting area.

In the foregoing liquid crystal display device, it is preferable that aninsulation film having an opening is formed on at least one of thesubstrates, and the first contact pads or the second contact pads isprovided in the opening.

In the case where the insulation film is not formed, in the area whichis not required to be electrically connected via the conductiveparticles, it is necessary to conserve the gap between the wires (i.e.,the gap between the adjacent transfer sections) greater than thediameter of the conductive particles so as to avoid leakage between thewires.

However, with the foregoing arrangement, it is possible to electricallyconnect the first contact pads and the second contact pads only via theconductive particles which are distributed in the opening. By thusforming the insulation film in the area which is not required to beelectrically connected via the conductive particles, it becomes possibleto reduce the gap between the wires smaller than the diameter of theconductive particles. This makes it possible to also reduce the routingwiring section in the input terminal, thereby realizing a liquid crystaldisplay device having a smaller frame without inducing leakage betweenthe wires via the conductive particle. Further, it also becomes possibleto suppress leakage between the wires in the adjacent transfer sectionseven when the conductive particles are agglutinated.

In the foregoing liquid crystal display device, it is preferable thatthe conductive particles is elastic.

With the foregoing structure, when two opposed substrates are bonded andfixed, the conductive particles having elasticity is deformed to someextent between the substrates. This makes it possible to conserve aplenty of contact area for the first contact pads and the second contactpads, thereby ensuring desirable electrical conductivity. Consequently,it is possible to reduce the contact resistance between the firstcontact pads and the second contact pads, thereby suppressing bluntingof signal which is sent to the second signal wiring.

In the foregoing liquid crystal display device, it is preferable thatthe conductive particles has a round shape and its diameter is greaterthan the cell thickness of the sealing section.

With the structure, the conductive particles electrically connect thefirst contact pads and the second contact pads when the conductiveparticles are slightly deformed. Therefore, it is possible to maintainthe electrical connection even when the cell thickness: the gap betweenthe substrates varies or changes. This realizes a stable electricalconnection, and provides stability against the variations or changes ofthe cell thickness.

In the foregoing liquid crystal display device, it is preferable thatthe conductive particles are provided only in the area at or 50 μm fromthe interface between the liquid crystal layer and the sealing section.

Commonly, in comparison with STN-LCD, a voltage-hold type liquid crystaldisplay element which is used for an active matrix liquid crystaldisplay device shows great degradation of image quality caused bydegradation with time of the voltage-hold capability for liquid crystal.The degradation with time of the voltage-hold capability for liquidcrystal is caused by elution of the impurity from the sealing material,ionization of ion, or other reason.

However, with the foregoing arrangement, it is possible to prevent thedecrease of voltage-hold capability for liquid crystal and thenon-uniform display occurred near the sealing section which are causedby elution of the impurity from the sealing material, or ionization ofion. Therefore, the degradation with time of voltage-hold capability forliquid crystal is prevented, thereby making it possible to provide aliquid crystal display with stable reliability.

The embodiments and concrete examples of implementation discussed in theforegoing detailed explanation serve solely to illustrate the technicaldetails of the present invention, which should not be narrowlyinterpreted within the limits of such embodiments and concrete examples,but rather may be applied in many variations within the spirit of thepresent invention, provided such variations do not exceed the scope ofthe patent claims set forth below.

What is claimed is:
 1. A liquid crystal display device, comprising: aswitching element substrate comprising a plurality of switchingelements; a counter substrate opposite to the switching elementsubstrate; a liquid crystal layer formed between the substrates; asealing section provided so as to enclose a display area between thesubstrates for sealing liquid crystal of the liquid crystal layer; afirst signal wiring, provided on one of the substrates for controllingthe switching elements; a second signal wiring, provided on the othersubstrate so as to be opposite to the first signal wiring for applying avoltage to the liquid crystal layer; at least one transfer section forelectrically connecting the first signal wiring or the second signalwiring and the substrate opposite to the first signal wiring or thesecond signal wiring, wherein said transfer section comprises both firstand second types of particles, said first type of particles in saidtransfer section being conductive and having greater flexibility andgreater size than said second type of particles in said transfersection, so that said first type of particles in said transfer sectionis for electrically connecting the first signal wiring or the secondsignal wiring and the substrate opposite to the first signal wiring orthe second signal wiring, and said second type of particles is forspacing the substrates from one another; wherein the transfer sectionincludes (a) a first contact pad, provided on a first substrate which isone of the substrates and has an input terminal of the first signalwiring and an input terminal of the second signal wiring, which isconnected to one of the first signal wiring and the second signal wiringprovided on the first substrate, (b) a second contact pad, provided on asecond substrate which is the other substrate, which is connected to theother one of the first signal wiring and the second signal wiring on thesecond substrate (the other substrate), and (c) the conductive particlesconnected to the first contact pad and the second contact pad; andwherein the transfer sections are provided alternately along both edgesof a width in the sealing section, and a width of the second signalwiring is narrower than that of the second contact pad.
 2. The liquidcrystal display device set forth in claim 1, wherein: an input terminalof the first signal wiring and an input terminal of the second signalwiring are provided on one of the substrates.
 3. The liquid crystaldisplay device set forth in claim 2, wherein: the transfer sectionincludes (a) a first contact pad, provided on a first substrate which isone of the substrates and has the input terminal of the first signalwiring and the input terminal of the second signal wiring, which isconnected to one of the first signal wiring and the second signal wiringprovided on the first substrate, (b) a second contact pad, provided on asecond substrate which is the other substrate, which is connected to theother one of the first signal wiring and the second signal wiring on thesecond substrate (the other substrate), and (c) the conductive particlesconnected to the first contact pad and the second contact pad.
 4. Theliquid crystal display device set forth in claim 3, wherein: the firstand second contact pads have substantially a same resistance.
 5. Theliquid crystal display device set forth in claim 4, wherein: thetransfer section is provided (a) between the first signal wiring and afirst signal generation circuit which provides a signal to the firstsignal wiring, or (b) between the second signal wiring and a secondsignal generation circuit which provides a signal to the second signalwiring.
 6. The liquid crystal display device set forth in claim 3,wherein: the transfer section is provided (a) between the first signalwiring and a first signal generation circuit which provides a signal tothe first signal wiring, or (b) between the second signal wiring and asecond signal generation circuit which provides a signal to the secondsignal wiring.
 7. The liquid crystal display device set forth in claim3, wherein: the first substrate is the switching element substratehaving the switching elements.
 8. The liquid crystal display device setforth in claim 3, wherein: the input terminal of the first signal wiringand the input terminals of the second signal wiring are made of aconductive material whose resistance is smaller than that of the firstsignal wiring or the second signal wiring formed on the secondsubstrate.
 9. The liquid crystal display device set forth in claim 3,wherein: an insulation film having an opening is formed on at least oneof the substrates, and the first contact pad or the second contact padis provided in the opening.
 10. The liquid crystal display device setforth in claim 1, wherein: the conductive particles have elasticity. 11.The liquid crystal display device set forth in claim 10, wherein: theconductive particles have round shapes and diameters which are greaterthan a cell thickness of the sealing section.
 12. The liquid crystaldisplay device set forth in claim 1, wherein: the conductive particlesare provided only in an area which is 50 μm or more far from aninterface between the liquid crystal layer and the sealing section. 13.The liquid crystal display device set forth in claim 1, wherein: theconductive particles are coated with a conductive material.
 14. Theliquid crystal display device of claim 1, wherein said first type ofparticles is formed by coating respective surfaces of elastic particleswith a conductive material, and said second type of particles comprisesglass fiber.
 15. The liquid crystal display device of claim 1, whereinsaid sealing section is formed by mixing said first and second types ofparticles into a thermosetting material in predetermined proportions.16. The liquid crystal display device of claim 1, wherein said sealingsection is formed by applying a thermosetting material, to which saidfirst and second types of particles are mixed, on one of the substrates,said one of the substrates is mated to the other of the substrates, andthese mated substrates are pressurized at a pressure for deforming thefirst type of particles so that the first type of particles is deformedto a thickness approximately equal to a cell thickness defined by thesecond type of particles.
 17. A liquid crystal display device,comprising: a switching element substrate comprising a plurality ofswitching elements; a counter substrate opposite to the switchingelement substrate; a liquid crystal layer formed between the substrates;a sealing section provided so as to enclose a display area between thesubstrates for sealing liquid crystal of the liquid crystal layer; afirst signal wiring, provided on one of the substrates for controllingthe switching elements; a second signal wiring, provided on the othersubstrate so as to be opposite to the first signal wiring for applying avoltage to the liquid crystal layer; at least one transfer section forelectrically connecting the first signal wiring or the second signalwiring and the substrate opposite to the first signal wiring or thesecond signal wiring, wherein said transfer section comprises both firstand second types of particles, said first type of particles in saidtransfer section being conductive and having greater flexibility andgreater size than said second type of particles in said transfersection, so that said first type of particles in said transfer sectionis for electrically connecting the first signal wiring or the secondsignal wiring and the substrate opposite to the first signal wiring orthe second signal wiring, and said second type of particles is forspacing the substrates from one another; and wherein: a meandistribution, volume D of the conductive particles (piece)/mm² is withina range of 1000≧D>5/S, where an area of the transfer section in adirection parallel to the substrates is S mm².
 18. The liquid crystaldisplay device set forth in claim 17, wherein: the transfer sectionincludes (a) a first contact pad, provided on a first substrate which isone of the substrates and has an input terminal of the first signalwiring and an input terminal of the second signal wiring, which isconnected to one of the first signal wiring and the second signal wiringprovided on the first substrate, (b) a second contact pad, provided on asecond substrate which is the other substrate, which is connected to theother one of the first signal wiring and the second signal wiring on thesecond substrate (the other substrate), and (c) the conductive particlesconnected to the first contact pad and the second contact pad.
 19. Theliquid crystal display device set forth in claim 18, wherein: the firstand second contact pads have substantially a same resistance.
 20. Theliquid crystal display device set forth in claim 19, wherein: thetransfer section is provided (a) between the first signal wiring and afirst signal generation circuit which provides a signal to the firstsignal wiring, or (b) between the second signal wiring and a secondsignal generation circuit which provides a signal to the second signalwiring.
 21. The liquid crystal display device set forth in claim 18,wherein: the transfer section is provided (a) between the first signalwiring and a first signal generation circuit which provides a signal tothe first signal wiring, or (b) between the second signal wiring and asecond signal generation circuit which provides a signal to the secondsignal wiring.
 22. The liquid crystal display device set forth in claim18, wherein: the first substrate is the switching element substratehaving the switching elements.
 23. The liquid crystal display device setforth in claim 18, wherein: the input terminal of the first signalwiring and the input terminal of the second signal wiring are made of aconductive material whose resistance is smaller than that of the firstsignal wiring or the second signal wiring formed on the secondsubstrate.
 24. The liquid crystal display device set forth in claim 18,wherein: an insulation film having an opening is formed on at least oneof the substrates, and the first contact pad or the second contact padis provided in the opening.
 25. The liquid crystal display device setforth in claim 17, wherein: the mean distribution volume D is within arange of 600≧D>5/S.
 26. The liquid crystal display device set forth inclaim 25, wherein: the mean distribution volume D is within a range of400≧D>5/S.
 27. A liquid crystal display device, comprising: a switchingelement substrate comprising a plurality of switching elements; acounter substrate opposite to the switching element substrate; a liquidcrystal layer formed between the substrates; a sealing section providedso as to enclose a display area between the substrates for sealingliquid crystal of the liquid crystal layer; a first signal wiring,provided on one of the substrates for controlling the switchingelements; a second signal wiring, provided on the other substrate so asto be opposite to the first signal wiring for applying a voltage to theliquid crystal layer; at least one transfer section for electricallyconnecting the first signal wiring or the second signal wiring and thesubstrate opposite to the first signal wiring or the second signalwiring, wherein said transfer section comprises both first and secondtypes of particles, said first type of particles in said transfersection being conductive and having greater flexibility and greater sizethan said second type of particles in said transfer section, so thatsaid first type of particles in said transfer section is forelectrically connecting the first signal wiring or the second signalwiring and the substrate opposite to the first signal wiring or thesecond signal wiring, and said second type of particles is for spacingthe substrates from one another; and wherein said at least one transfersection has a staggered structure.